The story is set in a world where some souls, rather than passing on after death, are recruited into the Department of Hauntings and Spirits, a bureaucratic afterlife with various offices: Grim Reapers, Guardian Angels, Poltergeists, and others. Tensions run deep between the Reapers, who collect souls marked for death, and the Guardians, who protect mortal life.
Darcy, the narrator, died in 1918 at 27 after a childhood spent in hospitals. She expected death to end her suffering, but instead she was made a Grim Reaper. A century later, she is exhausted by endlessly watching people die. She confides in Aelia, a fellow Reaper who appears as an eight-year-old girl but is one of the department's most powerful spirits. Aelia dismisses the concern. Still dissatisfied, Darcy enters the assignment room, where a massive yew tree grants each Reaper the soul they must collect. She whispers a plea for something different, eats one of the tree's poisonous berries, and receives a vision: a young man with dark hair, cracked glasses, wet pavement, and a flickering neon sign.
Her magic transports her to Annapolis, Maryland, where she finds the bar from her vision. The bartender, Gabriel, proposes a game: If he guesses her ideal drink, she must keep him company for his shift. He makes her a sidecar, and she loves it. Later, they share a cigarette in the alley and kiss, but the kiss causes Darcy's death magic to flare. Gabriel recognizes it and summons his own gray wings and a sword from his forearm tattoo. He identifies her as a Reaper; she identifies him as a Guardian Angel. Furious, he demands to know whose soul she has come to collect. Darcy insists she does not yet know and storms away.
Darcy secures a dilapidated town house and rescues a gravely injured German shepherd from a nearby alley, smuggling him through the department's intake system and naming him Tater Tot. When Gabriel confronts her the next morning, she reveals her true intention: She plans to save the soul she was sent for, not claim it. She proposes a deal. She carries a list of experiences she never had while alive; for each item Gabriel helps her cross off, she will share one clue from her vision. Gabriel agrees but privately intends to use the arrangement to identify the endangered soul. Twice before, he failed to protect souls from Reapers, and his superiors carved two scars across his chest with his own sword. A third failure will cost him his wings.
When Gabriel's friend Nate, a lanky, bespectacled young man, steps into the bar's back hallway one evening, Darcy's magic surges in recognition. Nate is the soul from her vision. She decides not to tell Gabriel, fearing he will shut her out and try to protect Nate alone.
Their list items draw them closer. Gabriel drives Darcy to a boat ramp for a river swim. She begins visiting the flower shop of Frank, an elderly bar regular who shares his grief over his late wife. One evening, they get drunk together in Gabriel's apartment, trading vulnerabilities. Gabriel explains that his tattoos appear whenever he moves on from a place, marking lives he has touched. Darcy sleeps in his bed and leaves a Post-it note with her next clue: cracked glasses. Meanwhile, Aelia visits to warn Darcy that her magic is becoming traceable and agrees to plant false traces to buy time.
After days apart, Gabriel takes Darcy by boat to a lighthouse in the Chesapeake Bay. As the sun rises, he confesses he cannot stop thinking about her, that he wants her in his bar and in his bed, and that he wants to be the one who gives her everything she wants. They kiss at the top of the lighthouse, surrendering to their feelings.
On the return trip, a storm rolls in. Back on shore, Nate scrambles along the wet cobblestones in rain-spattered glasses, and a speeding SUV rounds the corner. Gabriel is too far away. Darcy sprints from the bar porch and shoves Nate clear, taking the impact herself. Gabriel carries her upstairs and tends to her wounds. Darcy confesses she has known since she first met Nate that he was her assigned soul. Gabriel is angry but tells her it is done.
Rafe, an elder Guardian, warns Gabriel that Gideon, the ancient and long-absent head of all Grim Reapers, has returned due to irregularities in Annapolis. Shortly after, Brad, a Ferryman, or soul-transport officer, appears at the bar searching for Darcy. She and Gabriel hide from him, and the encounter draws them into greater physical intimacy, their magic intertwining.
At Frank's flower shop, Darcy's panic at spotting Brad outside triggers her suppressed magic, which erupts and kills every flower in the shop. Frank recognizes Darcy as the Reaper who collected his wife and young daughter after a car accident decades earlier. Trapped under the wreckage and close enough to death to see Darcy, he had begged her not to take them. Devastated, he orders her out. Darcy retreats to her town house, where her magic spirals out of control. Gabriel fights through the energy to reach her and absorbs her power, stabilizing her. He tells Darcy he has fallen in love with her, and their relationship is fully consummated.
Darcy encounters Gideon on a bench in front of the ice cream shop. He delivers an ultimatum: She must bring him Nate's soul, or he will collect it himself. Darcy begins withdrawing from Gabriel, insisting they must be realistic about their borrowed time. Gabriel refuses to accept this and declares his love. Darcy relents, though she secretly plans to offer herself to Gideon in Nate's place. She visits Frank to make amends, telling him she glimpsed where his family went: a beach with crashing surf and a rock formation his daughter called a window to a fairy world. Frank is moved to tears.
On Halloween night, Darcy takes Nate to a graveyard, intending to summon Gideon and offer herself in exchange. Gabriel, Aelia, and Frank all arrive. Gideon rejects Darcy's offer of her immortal soul, then her memories. Gabriel offers his wings. Frank steps forward and volunteers himself, telling Gideon he is an old man who wants to rest and see his family. Darcy accepts, realizing death can be an act of mercy. She takes Frank's hand, taps her scythe, and they vanish.
At the department, Gideon opens the door behind the intake desk, and the sound of surf fills the room. Frank, restored to his younger self, steps onto the beach, where his daughter runs to embrace him. Gideon places Darcy on administrative leave for 28 days.
Back in Annapolis, Rafe removes Gabriel's wings painlessly, making him mortal. He reveals that the scars on Gabriel's chest were never punishments but marks from times he came close to his soulmate and lost her. Every tattoo represents a life Gabriel shaped on his path toward Darcy. His entire existence as a Guardian was about finding her.
After 28 days, Gideon reinstates Darcy and presents her with a final berry. Her actions, he explains, demonstrated the Reapers' true purpose: not to end life but to grant mercy. Darcy eats the berry, and her vision unfolds: a rumpled bed with flannel sheets and a man with dark hair, faded tattoos, and smile lines, older but unmistakable. It is Gabriel, aged into a long mortal life. This is the last soul she will ever claim.
Darcy returns to the bar and finds Gabriel in the back hallway. He thinks she is a daydream. She touches his face, and he realizes she is real. She tells him this is her final assignment and promises him all her minutes, every last one. When he asks what they should do with their time, Darcy smiles and says she will make a list.